1. Field of the Invention
This invention relates to a photoresponsive material having a novel dye compound, and more specifically, to a photoresponsive material containing a dye as a spectral sensitizer having a cyclodextrin or its derivative as a substituent.
2. Description of the Prior Art
Dyes have been used in photoresponsive materials for various purposes. One of these is use for spectral sensitization.
Since the technique of spectral sensitization by using a dye was discovered in the field of silver salt photography by H. W. Vogel in 1873, this technique has greatly developed as one of the important techniques. In the field of photoelectromotive force as well, application of this technique to various types of electrodes has been studied since Sheppard et al. published a study performed using a silverbromide electrode in 1940. In order to extend the range of light wavelength in which a photoresponsive material is responsive or restrict the range to a desired region, spectral sensitization of the material is a very important technique in the field of photoresponsive materials. Based on this background, fundamental and applied research into spectral sensitization have been extensively conducted. Among this research, elevation of the efficiency of spectral sensitization was very interesting from the view point of practical application of the technique.
One method for increasing the efficiency of spectral sensitization was to increase the amount of light utilized by increasing the amount of the dye contained in the material so as to increase its light absorptivity. In this method, it was a matter of course that the light absorptivity of the material could be increased by increasing the amount of the dye used for spectral sensitization. But, it was disappointing that the efficiency of spectral sensitization did not always elevate in proportion to the amount of the dye but it began to decrease after it exceeded a certain point. This fact was well known since it was first reported by Leermakers et al. in 1937. Then, a special method was proposed to solve this dilemma by using spectral sensitizing dyes coupled in advance in order and so arranged that the more remote the dye is from substrate, the higher the absorptivity to short wavelength light is, in order to increase the amount of light absorbed by the material and utilized for its spectral sensitization (in U.S. Pat. Nos. 3,622,317, 3,976,493 and 3,976,640).
The above conventional method was achieved by contriving a new arrangement of dyes but was not necessarily satisfactory for spectrally sensitizing a specific range of wavelengths of light. Therefore, it has been strongly demanded to develop a photoresponsive material the spectral sensitivity of which is elevated by a novel spectral sensitizer contained therein.